Interpretive Summary: Many dairy producers in the northcentral United States have a critical need for windows of opportunity to distribute animal manures during the summer months rather than relying heavily on spring or fall application strategies that bookend production of corn. This is especially true for cleaning bedded-pack pens typically housing replacement heifers or dry cows, or well bedded pens maintained specifically for calving. Forage production strategies that utilize fall-grown oat allow opportunities for hauling during midsummer, when wet field conditions and time stress may be less problematic for dairy producers. In this trial, we compared production of fall-grown oat forages fertilized with urea or bedded-pack manure obtained from a dairy heifer-rearing facility. The bedded-pack manure used in this trial contained wooden shavings as the principal bedding material, and it exhibited no evidence of contributing significantly to forage growth, resulting in apparent nitrogen use efficiencies that were sometimes negative, thereby suggesting soil nitrogen was immobilized. Generally, the nutritive value of oat forages harvested after receiving bedded-pack manures as soil amendments compared closely to oat forages harvested from unfertilized control plots; however, forages fertilized with urea exhibited consistent growth responses to applications of a much more available nitrogen source for supporting forage growth. Producers should not expect bedded-pack manures of this type to increase yields of fall-grown oat within the production year; any benefits will likely be realized for subsequent crops and years.

Technical Abstract:
Previous research has shown that oat (Avena sativa L.) has promise as a fall-forage option for dairy producers. In addition, dairy producers often have a recurring need to identify opportunity windows for manure hauling other than before or after production of corn (Zea mays L.). Our objectives were to evaluate the effects of N fertilization, cultivar selection, and harvest date on dry matter (DM) yield, N uptake, N recovery, and the nutritive value of fall-grown oat forages fertilized with either urea (46-0-0) or bedded-pack manure obtained from a dairy-heifer facility. Two cultivars of oat (ForagePlus and Ogle) were planted in August 2011 and 2012, fertilized with bedded-pack manure (23 or 45 Mg ha-1; wet basis) or commercial urea (46-0-0) at rates of 0, 20, 40, 60, or 80 kg N ha-1, and then harvested on two dates. Climatic conditions differed sharply across years, with growth responses limited by droughty conditions during 2012. During both years, DM yield increased linearly with commercial N fertilization, although the magnitude of these responses was relatively small. Yields of DM following applications of urea exceeded those of forages receiving bedded-pack manure during 2011. Apparent N-recoveries increased linearly with application rate for urea during 2011, and increased with both linear and quadratic effects during 2012, but N-recoveries following applications of bedded-pack manures were minimal during both years (overall range = -6.2 to 2.6% of N applied). These results indicate that bedded-pack manures containing wooden shavings provided little immediately available N to support production of fall-grown oat.